Breath warming devices

ABSTRACT

This invention pertains to breath warming devices and particularly of the self contained type wherein heat and moisture from the exhaled breath is utilized to warm and humidify the ensuing inhaled breath. Under arctic conditions air of temperature as low as minus 50 degrees F. may be inhaled. Under such conditions approximately 44 percent of the total heat generated within the body is lost through breathing. Previous attempts to develop self contained breath warming devices have met with discouragement because at low ambient temperatures ice and frost formation tends to block the air flow and render the device inoperable. The subject invention discloses a design which is free of such difficulty. The design employed in the device incorporates an automatic valve which opens responsive to increasing air friction within the device when frost or ice begin to obstruct the air flow therethrough. The valve operates only to bypass a portion of inhalation air while leaving the flow and volume of exhaled air unaffected. The amount of heat recovered from exhalation thus remains constant whereas the demand for heat to warm inhaled air is decreased when ice begins to form in the unit. Due to this change in heat balance further ice does not form, and the device remains operative despite very low ambient temperature. Also shown are additional features of novel nature particularly related to improvement of means for effecting efficient and comfortable mounting and fit of the device relative to the face of the wearer.

United States Patent [19] Turner [451 Sept. 17, 1974 [21] Appl. No.: 199,141

[52] US. Cl. 128/212 [51] Int. Cl A6lm 16/00 [58] Field of Search..... 128/212, 141, 142.4, 142.6,

[56] References Cited UNITED STATES PATENTS 603,021 4/1898 Dight 128/212 2,827,900 3/1958 Marietta 128/146.7

2,939,458 6/1960 Lundquist 128/146 3,037,501 6/1962 Miller 128/146 X 3,326,214 6/1967 McCoy 128/212 3,491,754 1/1970 Weese 128/212 FOREIGN PATENTS OR APPLICATIONS 1,364,599 5/1964 France 128/212 317,213 8/1929 Great Britain 128/212 Primary Examiner-Richard A. Gaudet Assistant Examiner-G. F. Dunne Attorney, Agent, or FirmWo1f, Greenfield & Sacks [57] ABSTRACT This invention pertains to breath warming devices and particularly of the self contained type wherein heat and moisture from the exhaled breath is utilized to warm and humidify the ensuing inhaled breath. Under arctic conditions air of temperature as low as minus 50 degrees F. may be inhaled. Under such conditions approximately 44 percent of the total heat generated within the body is lost through breathing.

Previous attempts to develop self contained breath warming devices have met with discouragement because at low ambient temperatures ice and frost formation tends to block the air flow and render the device inoperable. The subject invention discloses a design which is free of such difficulty. The design employed in the device incorporates an automatic valve which opens responsive to increasing air friction within the device when frost or ice begin to obstruct the air flow therethrough. The valve operates only to bypass a portion of inhalation air while leaving the flow and volume of exhaled air unaffected. The amount of heat recovered from exhalation thus remains constant whereas the demand for heat to warm inhaled air is decreased when ice begins to form in the unit. Due to this change in heat balance further ice does not form, and the device remains operative despite very low ambient temperature. Also shown are additional features of novel nature particularly related to improvement of means for effecting efficient and comfortable mounting and fit of the device relative to the face of the wearer.

2 Claims, 8 Drawing Figures BREATH WARMING DEVICES This invention relates to breath warming devices, and more specifically to that type of such device which captures and utilizes the heat and moisture from an exhaled breath to warm and humidify the following inhaled breath of cold air.

Under Arctic conditions protection of the body and respiratory tract from cold has long presented a serious problem. Efficient clothing has been developed to effectively limit heat loss from the surface of the body, but regardless of the warmth of clothing worn, a large amount of additional heat is lost through breathing. At an ambient temperature of minus 50 F. this loss approximates 44 percent of total heat generated by the body.

Body heat is produced through oxidation of food stored in the blood stream. Required oxygen is supplied by respiration. If heat needs are above normal the intake of oxygen must be greater than normal, which necessitates heavy breathing. Unfortunately heavy breathing of cold air tends to damage the respiratory tract. In attempt to protect the lungs the exposed person may then resort to shallow breathing, which deprives the system of needed oxygen and consequently the generation rate of body heat decreases. When the production of heat fails to meet the body demand for warmth and energy bodily chill, freezing of extremities, and even death may result.

In previous attempts to provide protection for the respiratory tract devices requiring external heat supply have been constructed. In addition to drawbacks of size, weight and cost a serious defect inherent in such types is that failure or exhaustion of the heat source leaves the user entirely unprotected. Various arrangements also have been made to recover heat from the exhaled breath. Heretofore a problem inherent in such units has been that at temperatures appreciably below zero deg. F. ice forms in the exchanger unit to obstruct air flow and make the device inoperative just at the time when the need for protection is the greatest.

In addition to the above a common problem in all respiratory devices where there is required a close seal around the nose and mouth area of the user lies in the difficulty of providing an arrangement sufficiently flexible and adaptable to fit comfortably a wide range of facial configurations. Additional requirements are that such a device should be light in weight, low in cost, and of relatively unbreakable construction.

To satisfy the foregoing and other related requirements the first objective of the present invention is to provide a sturdy and light weight self contained breath warming device which will effectively warm and humidify each inhaled breath by utilizing heat and moisture retrieved from the preceding exhaled breath.

The second objective of the invention is to provide means to avoid ice formation in the device and to insure satisfactory operation at very low ambient temperatures such as minus 50.

The third objective of the invention is to include an improved arrangement to provide an effective and comfortable air seal around the oral-nasal area of the wearer which is adaptable to a wide range of facial configurations.

The fourth objective of the invention is to provide a device which may readily be emplaced or removed as required, which may quickly and easily be be be dismantled for cleaning or sterilization, and which provides for the lower portion of the face protection against cold air and wind.

To achieve the first objective of the invention I provide for mounting adjacent the nose and mouth of the wearer a semi-rigid oral-nasal housing within which is fixed a porous heat sink-exchanger pack. In my pre-.

ferred design this pack is composed of metallic filiament surrounded for protective purpose with woven plastic mesh plus a metal shield open at opposite ends. The heat capacity of material in this pack is designed to be such that the heat from one exhalation (approximately 0.2 B.T.U.) may be absorbed with a temperature rise of the metallic material of less than 5 F. To attain the desired rapid rate of heat exchange between the heat sink metallic material and the air passing therethrough the total required surface area of filiament within the pack is calculated to approximate 300 square inches.

A further important requirement of the design is that the total volume within the oral-nasal housing be kept to a minimum to avoid unnecessary entrapment and recycle of exhaled air. In the embodiment hereinafter described I limit this volume to a maximum of 5 cubic inches.

To achieve the second objective of the invention I arrange to prevent harmful ice formation within the device by use of a simple and novel expedient. When ice first starts to form at the cold air entrance the resistance to air flow through the heat sink-exchanger pack increases. I now provide an inhalation by-pass valve. When the resistance to air flow through the pack increases to about one-eighth inch of water differential this by-pass valve opens to admit some cold air directly into the plenum space at the warm air end of the heat sink-exchanger pack. Due to this by-passed volume the residual volume of inhaled air passing through the pack is reduced, and consequently the demand for heat from the pack is less. The heat delivered by exhaled air to the pack remains undiminished because operation of the valve is such to insure that all exhaled air continue to pass through the heat sink-exchanger. It may be seen that the heat balance within the pack is thus automatically altered so further ice build up does not occur. This arrangement has proved effective under test at very low temperatures. It is a salient feature of this invention.

To achieve the third objective of the invention I have designed a novel arrangement to provide a comfortable air seal about the nose and adjacent facial areas. Since the human nose may vary widely in size and cross section, I provide in the semi-rigid housing before mentioned a horse-shoe shaped opening of size and configuration freely to surround the cross section of a large human nose. At its open end this opening is made adjustable in width so it may easily be dimensionsed to fit lightly across the width of the nose at the face line. The horse-shoe shaped opening is now partially closed with a thin flexible elastic nose seal membrane of material such as latex. This membrane is provided with an arch shaped cutout of size and shape to fit closely over the small sized human nose. The elasticity of the membrane will allow it to stretch to fit the medium or large sized nose. In assembly of the device this membrane is shaped in a compound curvature as later described. This elasticity and curvature comprise important features of the invention in that a comfortable air seal that all exhaled air should pass through the heat sinkexchanger pack, but that some by-pass of inhaled air around the pack is not only permissible but actually desireable and essential at very low ambient temperatures. Because of its unique design and contribution to the over-all effective functioning of the invention, it is submitted that this air seal arrangement is of patentable nature.

To achieve the fourth objective of the invention I have provided a heat sink-exchanger pack constructed as a separate unit and mounted within the oral-nasal housing in manner to be readily removed for cleaning. A flexible face protector is removeably attached to the housing by means of a mounting and adjustment spring. A single screw holds the heat sink-exchanger pack, the oral-nasal housing and the face protector in assembled relationship. Elastic head and neck bands hold the unit in position for use on the face of the user.

The accompanying drawings and description cover a preferred form of the invention. It is to be understood that variations of the features shown may be utilized within the scope of the invention FIG. I Shows front and side views of the invention as worn complete with face protector and holding straps.

FIG. II Shows front and side views of the oral-nasal housing as in FIG. I with the face protector removed.

FIG. III Shows top, side and cross section views of the heat sink-exchanger pack.

FIG. IV Shows side, top, bottom and rear views of the oral-nasal housing with the heat sink-exchanger assembled therein.

FIG. V Is a perspective sketch of the elastic nose seal membrane as shaped in assembly.

FIG. VI Is a cross section view of the oral-nasal housing assembled complete with heat sink-exchanger pack, elastic nose seal membrane and inhalation by-pass valve.

FIG. VII Is an oblique view of the mounting and adjustment spring.

FIG. VIII Shows the cross section as in FIG. VI applied to the face of the user.

.The assembled device applied to the face of a user is shown in FIG. I. A flexible face protector 2 is held rearwardly and in contact with the face by back holding elastic 3 and is held upwardly by top support elastic 4. The length and tension of 3 may be varied with adjustment clip 13. A mounting and adjustment spring 5 which is positioned in assembly by screw 6 is shown in further detail in FIG. VII. Air is inhaled and exhaled via point 14. Shown in side and front view of FIG. II is the oral-nasal housing 1 as viewed with the face protector removed.

The functional performance of the invention may best be explained by reference to FIG. VI. which shows the assembly in cross section. Oral-nasal housing 1 has a horseshoe shaped opening in its upper end as shown in 4b of FIG. IV. In FIG. VI this opening is fitted with an elastic nose seal membrane 10. This membrane is detailed in FIG. V. When the unit is held in place against the face the elastic membrane makes air tight contact with the nose contour.

The side of housing 1 adjacent the wearers face is open. The padded edges 17 of the housing make substantially air tight contact against the wearer's face, thus it is seen that respiration results in air being inhaled or expelled via area 14. This will be better understood by referring to FIG. VIII. Area 14 is perforated as shown in 4c of FIG. IV. Heat sink-exchanger pack 7 is shown detailed in FIG. III, where it is shown as comprising a porous heat sink element 7a, a face plate 12, and a side and back shield 19.

In FIG. VI pack 7 is shown installed in housing 1, being held in place by screw 6. In this view the front, rear and right hand surfaces of 7 make contact with the corresponding inner surfaces of housing 1. The left hand surface as shown is partially closed by plate 12 which has a cut-away portion 18 to expose an area of the porous material of heat sink-exchanger pack 7. The upper end 15 and lower end 14 of pack 7 are open to allow air passage.

The cross section as in FIG. VI is shown in FIG. VIII in relation to the human face. It will be noted that a plenum chamber 16 is defined by the upper end of housing 1, the nose and upper lip of the wearer, nose seal membrane 10, and the upper surface 15 of pack 7. During nasal respiration all air inhaled or exhaled passes through chamber 16. Exhaled air passes downward through pack 7 from area 15 to area 14 where it is released to the atmosphere. Inhaled air is normally drawn in at area 14 and passes upward to area 15 thence into plenum chamber 16, from which it enters the nostrils.

As illustrated, cut-away area 18 of face plate 12 is substantially blocked by the lips of the wearer. Sponge pad 11 seals the chin area. If mouth or oral breathing is resorted to air is inhaled and exhaled through area 18 to and from pack 7, and plenum chamber 16 does not then serve for air passage.

When the invention is in use at not lower than zero deg. F. and with nasal breathing, exhaled air passes downward through pack 7 giving up heat and moisture in transit to cause the temperature of the material in the heat sink to rise. On the following inhale cycle cold air is drawn in at area 14 and moves upward acquiring heat and humidity in transit until it emerges at area 15 with a temperature and humidity condition corresponding to about plus F. The air is then drawn into the lungs where additional heat and moisture is added to establish a heat and humidity saturation condition of approximately 98 F. At each respiration cycle this process is repeated.

As before stated, previous devices of this general type when used under ambient conditions appreciably lower than zero deg. F. are prone to freeze up and become inoperative due to frost and ice blockage of the intake area such as 14. An important feature of my invention lies in the following arrangement for prevention of freeze-up.

I have designed heat sink-exchanger pack 7 such that normally the'restriction to passage of air therethrough is extremely low. With ordinary breathing the air pressure in plenum chamber 16 varies only in the order of one-sixteenth inch of water difierential above and below the existing barometric pressure. Now when ice formation starts to restrict area 14 this differential pressure range increases. When on the inhale cycle a differential of one-eighth inch of water below atmospheric pressure is reached inhalation bypass valve 9 opens to allow some cold air to pass from the atmosphere through inhalation by-pass apeture 8 directly into plenum chamber 16. Due to this by-passed volume less air now passes through heat sink-exchanger 7 during the inhale cycle and therefore the amount of heat extracted is reduced. During the subsequent exhale cycle valve 9 moves to close apeture 8 and therefore the entire volume of exhaled air is forced downward through pack 7 imparting thereto a normal amount of heat and moisture. It may now be seen that when ice first starts to form in area 14 valve 9 functions to alter the air flow and the heat balance in heat sink-exchanger 7 with the result that further ice formation is prevented and the invention will continue to operate satisfactorily.

In summary, the function of inhalation by-pass valve 9 is to insure against objectionable icing by automatically and as required reducing the damand for heat to warm the inhaled air while allowing a normal amount of exhaled heat to be available to maintain non-icing conditions within the heat sink-exchanger.

It may be stated that in a device of this type the air seal means around the nose and mouth area of the wearer should be such to insure that all exhaled air pass at all times through the heat sink-exchanger pack. Under some conditions as above disclosed, it is not only desireable but essential that by-pass of some inhalation air around said pack be allowed. This brings us to discussion of elastic nose seal membrane 10. For reasons of utility and user comfort this membrane must apply only slight pressure against the nose surface, and since such pressure must be minimal a certain amount of air leakage may inadvertently occur. In view of the fact that as just analyzed exhalation leakage must be minimized while some inhalation leakage may be allowable, I have elected to so shape membrane 10 that its free edge and adjacent surface comprises a flap lying in downward direction along the nose surface in manner such that attempt of air to escape from plenum chamber 16 will cause this flap to fit more closely against said nose surface and thus to have a self sealing effect against the leakage of air. Inward leakage of air may be somewhat less inhibited, and in fact with careful design and adjustment the flap effect of membrane 10 may be caused to serve the function of an inhalation by-pass valve and a separate valve such as 9 might be eliminated.

To aid in the adjustment of the fit of membrane 10 relative to the nose of the user mounting-adjustment spring 5 serves a purpose. Referring to FIG. VII, this spring may be bent so that distance 20 is such that when the entire invention is assembled housing 1 is distorted to cause distance 21 of FIG. IV to become optimum for lateral fit to the nose of the wearer.

Having thus revealed my invention, what I claim herein is:

1. In a breath warming device of the self contained type wherein heat and moisture from an exhaled breath is used to warm and humidify the ensuing inhaled breath, said device having a heat sink-exchanger pack through which exhaled air is caused to pass to impart heat thereto and to deposit moisture therein and through which in opposite direction the subsequent breath of inhaled air is caused to pass to absorb heat and moisture therefrom, said device including an oralnasal housing having walls and at least partially open ends and being adaptable to the passage of air therethrough, said housing having mounted therein and adjacent one end thereof said heat sink-exchanger pack and having the opposite end thereof constructed as a plenum chamber adapted to provide respiratory association with the oral-nasal area of the human face, that improvement which comprises an inhalation by-pass aperature adaptable to allow movement of ambient air into said plenum chamber, said aperature being selectively closed by a moveable inhalation by-pass valve arranged in manner such that said valve will open responsive to differential air pressure to admit ambient air direct to said plenum chamber when and only when the air pressure within said chamber decreases to a predetermined value below ambient air pressure, such decrease in pressure being caused during inhalation cycle by increase in resistance to air flow through said heat sink-exchanger pack due to cause such as accumulation of frozen water vapor adjacent the inlet area of said pack.

2. A breath warming device as per claim 1 wherein the surface area of material within said heat sinkexchanger pack is substantially three hundred square inches and wherein the porosity of said material is such to offer approximately one sixteenth inch of water differential resistance to air flow therethrough during normal respiration rates. 

1. In a breath warming device of the self contained type wherein heat and moisture from an exhaled breath is used to warm and humidify the ensuing inhaled breath, said device having a heat sink-exchanger pack through which exhaled air is caused to pass to impart heat thereto and to deposit moisture therein and through which in opposite direction the subsequent breath of inhaled air is caused to pass to absorb heat and moisture therefrom, said device including an oral-nasal housing having walls and at least partially open ends and being adaptable to the passage of air therethrough, said housing having mounted therein and adjacent one end thereof said heat sink-exchanger pack and having the opposite end thereof constructed as a plenum chamber adapted to provide respiratory association with the oral-nasal area of the human face, that improvement which comprises an inhalation by-pass aperature adaptable to allow movement of ambient air into said plenum chamber, said aperature being selectively closed by a moveable inhalation by-pass valve arranged in manner such that said valve will open responsive to differential air pressure to admit ambient air direct to said plenum chamber when and only when the air pressure within said chamber decreases to a pre-determined value below ambient air pressure, such decrease in pressure being caused during inhalation cycle by increase in resistance to air flow through said heat sink-exchanger pack due to cause such aS accumulation of frozen water vapor adjacent the inlet area of said pack.
 2. A breath warming device as per claim 1 wherein the surface area of material within said heat sink-exchanger pack is substantially three hundred square inches and wherein the porosity of said material is such to offer approximately one sixteenth inch of water differential resistance to air flow therethrough during normal respiration rates. 